human bio

exam

validity

when an experiment tests what it’s supposed to

accuracy

refers to how close the data is to the exact value

reliability

the extent to which an experiment gives the same result each time it is performed

literature review

a thorough evaluation of existing research studies related to a specific topic or question, summarizing and synthesizing findings to identify gaps and trends.

steroid hormones

• lipid soluble

• when they reach target cells, they diffuse through cell membrane

• in the cytoplasm, they combine with receptor proteins to form hormone-receptor complex

• complex binds to DNA in nucleus.

• activate or inhibit specific genes, altering transcription

• new proteins or enzymes produced

• slow to start, long lasting

• testosterone or cortisol

protein/amine hormones

• water soluble

• attach to receptor proteins in the cell membrane of the target cell forming hormone-receptor complex

• complex forms secondary messenger substance

• substance diffuses through cell and activates certain enzymes

• rapid effect but short lasting

• insulin

how are the anterior pituitary and hypothalamus connected

blood vessels lying in the infundibulum

hypothalamus secretes releasing or inhibiting factors to stimulate or slow down the secretion of the hormone

anterior pituitary produces and secretes hormones

hormones produced and secreted by anterior pituitary

growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, prolactin, gonadotropins

how is the posterior pituitary and hypothalamus connected

• hormones are produced by the hypothalamus

• nerve fibres that come from nerve cell bodies in the hypothalamus

• the release of hormones is triggered by nerve impulses

posterior pituitary hormones

antidiuretic hormone, oxytocin

function of growth hormone

growth and protein synthesis of body cells

function of thyroid stimulating hormone

stimulates the production and release of hormones from the thyroid

function of adrenocorticotropic hormone

production and release of hormones from adrenal cortex

prolactin

milk production from mammary gland

thyroid gland- where is it found and what hormones does it produce and release

located in neck.

secretes thyroxine, triiodothyronine, calcitonin

hormones produced by adrenal medulla

adrenaline and noradrenaline

hormones produced by adrenal cortex

aldosterone and cortisol

pancreas- what is it (cells) and what hormones do these cells secrete

• made of clusters called islets of Langerhans- alpha and beta cells

• beta cells secrete insulin

• alpha cells secrete glucagon

thyroxine

controls body metabolism by regulating reactions in which complex molecules are broken down to release energy.

maintains body temperature due to energy being released- some in the form of heat

calcitonin

decreases the concentrations of calcium and phosphate in the blood by reducing the reabsorption of calcium by the kidneys and breakdown of bone.

adrenaline

helps prepare the body for a reaction to threatening situation concerned with fight or flight response

similar effect to that of sympathetic division of autonomic nervous system

noradrenaline

similar effect to adrenaline

increases rate and force of heartbeat

aldosterone

secreted in response to a decrease in concentration of sodium ions in blood, decrease blood volume or pressure.

acts on distal convoluted tubules and collecting ducts to increase the amount of sodium ions reabsorbed into the bloodstream

increase amount of potassium in urine

cortisol

promotes normal metabolism, helping body to withstand stress, repair damaged tissues

insulin

reduces amount of glucose in the blood by promoting the uptake of glucose from blood by:

• glycogenesis in the liver and skeletal muscles

• accelerate transport of glucose from blood to body cells, especially skeletal muscle

• stimulating conversion of glucose to protein - protein synthesis

• lipogenesis in adipose tissue

glucagon

increases blood glucose levels by:

• stimulate glycogenolysis in liver

• stimulate gluconeogenesis in the liver

• having a mild stimulating effect on protein breakdown

cell body of neuron

part of the neuron that contains the nucleus and is responsible for controlling the functioning of the cell.

dendrites

carry messages or nerve impulses into the cell body

axon

carries nerve impulses away from the cell body

myelin sheath

fatty material that covers the axon

myelin sheath functions

• acts as an insulator

• protects axon from damage

• speeds up the movement of nerve impulses along the axon

neurotransmitters

carries a nerve impulse across the synapse

sensory (afferent) neurons

carry messages from receptors in sensory organs, or skin to central nervous system

motor (efferent) neurons

carry messages from central nervous system to the effectors.

multipolar neurons

one axon and multiple dendrites extending from cell body

most common and includes most of interneurons in brain and spinal cord, motor neurons that go to skeletal muscles

bipolar neurons

one axon and one dendrite

occur in eye, ear and nose. take impulses from receptor cells to other neurons

unipolar

one extension and one axon

pseudounipolar neuron

single axon from cell body which separates into two extensions. one extension connects to dendrites while other ends in axon terminal

most sensory neurons that carry messages to spinal cord

extracellular fluid

fluid outside the cell, containing high amount of positive sodium ions and negative chloride ions.

intracellular fluid

fluid inside the cell

positive potassium ions

resting membrane potential

-70mV

potential of the inside of the membrane is 70mV less than of the outside.

sodium-potassium pump

uses active transport to move three sodium ions out of the cell for every 2 potassium ions that move in

action potential

the rapid depolarisation and repolarisation of the membrane

depolarisation

• increase in membrane potential.

• if stimulus by a neurotransmitter or sensory receptor is strong enough to increase potential to -55mV, then voltage gated sodium channels open.

• sodium ions move into the cell

• makes the inside of the cell more positive than the outside- 40mV

Repolarisation

• sodium channels close, stopping influx of sodium ions

• voltage gated potassium channels open, increasing flow of potassium ions out of the cell

• inside of cell more negative than outside

• decrease membrane potential

refractory period

once sodium channels have opened, they quickly become inactivated.

unresponsive to stimulus

for brief period, membrane will not undergo another action potential

lasts from -55mv until returns back to -70mV

conduction of a nerve impulse along Unmyelinated fibres

continuous conduction

dpeolarisation of the membrane causes a movement of sodium ions in adjacent areas, stimulating the opening of the voltage-gated sodium channels in the next part of the membrane.

The impulse travels relatively slowly because an action potential must be generated along each successive section of the membrane.

conduction of a nerve impulse along myelinated fibres

travels by saltatory conduction- the action potential travels along fibre by jumping from one node of ranvier to the next.

travel much faster along myelinated fibres

transmission across a synapse

1. when nerve impulse reaches the axon terminal, it activates the voltage-gated calcium ions channels.

2. calcium ions flow into the cell at the pre-synaptic axon terminal

3. this causes synaptic vesicles to fuse with the membrane, releasing neurotransmitters by exocytosis.

4. the neurotransmitters diffuse across the gap and attach to receptors on the membrane of the next neuron.

5. this stimulates ligand-gated protein channels to open, which allows the influx of sodium ions and initiates an action potential in the post-synaptic membrane.

receptor definition

able to detect a change in internal or externa environment; stimulus.

reflex

a rapid, autonomic repsonse to a change in the external or internal environment

properties of a reflex

1. a stimulus is required to trigger a reflex- not spontaneous

2. involuntary- without conscious thought

3. rapid- small number of neurons involved

4. stereotyped- same way each time.

comparison of nervous and endocrine systems

• nature of message: nervous- electrical impulses and neurotransmitters. Endocrine- hormones

• transport of message: nervous- along the membrane of neurons. Endocrine- by the bloodstream

• cells affected: nervous- muscle and and gland cells, other neurons. Endocrine- all body cells

• type of response: nervous- local and specific. Endocrine- general and widespread

• time taken to respond: nervous- rapid, within milliseconds. endocrine- slower from seconds to days.

• duration of response: nervous- brief- stops quickly when stimulus stops. endocrine- longer lasting- may continue long after stimulus has stopped.

three structures that protect the CNS

bone, meninges, cerebrospinal fluid

cranium

outermost protective layer of bone

dura mater

dura mater is tough and fibrous and the outer layer

sticks closely to bones in the skull

arachnoid mater

middle layer, loose mesh of fibres

pia mater

inner layer.

delicate

contains blood vessels and sticks closely to surface of brain and spinal cord

cerebrospinal fluid

clear, watery fluid

occupies a space between the middle and inner layers of meninges.

circulates through cavities in the brain and through canal in centre of spinal cord

three functions of cerebrospinal fluid

protection: acts as a shock absorber, cushioning any blows or shocks the CNS may sustain

support: the brain is suspended inside the cranium and floats in the fluid that surrounds it

transport: circulates around and through the CNS taking nutrients to cells of brain and spinal cord and carries their wastes.

cerebrum

• biggest part of the brain

• grey matter (cerebral cortex) on the outside.

• cerebral cortex is folded in patterns that increase surface area.

• convolutions - sulci- shallow. fissures- deep downfolds.

four lobes of the cerebral cortex

frontal, occipital, temporal, parietal, insula

frontal lobe functions

thinking, problem solving, emotions, personality, language, control of movement

parietal lobe functions

processing temperature, touch, taste, pain and movement

temporal lobe functions

processing memories and linking them with senses. receives auditory information

occipital lobe function

vision

insula

recognition of different senses and emotions, addictions and psychiatric disorders.

grey matter

neuron cell bodies, dendrites and unmyelinated axons

white matter

myelinated axons

corpus callosum

• lies underneath the cerebrum

• wide band of nerve fibres

• nerve fibres cross from one cerebral hemisphere to the other and allow the two sides of the cerebrum to communicate.

cerebellum

• lies under rear part of cerebrum

• surface folded into parallel ridges

• control over posture, balance, and the fine coordination of voluntary muscle movement

• all functions take place below conscious level

what would happen if our cerebellum became damaged.

movements would no longer be smooth and coordinated.

spasmodic and jerky

functions of the hypothalamus

• regulation of the autonomic nervous system- regulation of heart rate, blood pressure, secretion of digestive juices.

• body temperature

• food and water intake

• waking and sleeping patterns

• contractions of urinary bladder

• emotional responses

• secretion of hormones and coordination of the parts of the endocrine system

centres the medulla oblongata contains

• cardiac centre- regulates rate and force of heartbeat

• respiratory centre- controls rate and depth of breathing

• vasometer centre- regulates diameter of blood vessels

location of white and grey matter in spinal cord

grey matter is at the centre and surrounded by white matter.

functions of the spinal cord

carry sensory impulses up to brain and motor impulses down from brain.

integrate reflexes.

types of nerves

cranial and spinal nerves

cranial nerves

• 12 pairs

• most nerves are mixed nerves; sensory and motor fibres

• few carry one or the other.

spinal nerves

• 31 pairs

• all mixed nerves

• each nerve is joined to the spinal cord by the ventral root or dorsal dorsal

ventral root

contains axons or motor neurons that have their cell bodies in the grey matter of the spinal cord

dorsal root

contains axons of sensory neurons that have their cell bodies in small swelling on the dorsal root ganglion.

afferent division of PNS

• carry impulses into the CNS by sensory neurons from receptors in the skin and around muscles and joints

• somatic sensory neurons and visceral sensory neurons

somatic sensory neurons

bring impulses from skin and muscles

visceral sensory neurons

bring impulses from internal organs

efferent division of PNS

• carry impulses away from the CNS

• somatic and autonomic division

somatic motor neurons

impulses from CNS to the skeletal muscles

autonomic division of efferent division

• carries impulses from CNS to heart muscles, involuntary muscles and glands

• subdivided into sympathetic and parasympathetic

• regulated by groups of nerve cells in medulla oblongata, hypothalamus, cerebral cortex

compare the somatic and autonomic division of efferent division

effectors
autonomic: heart muscle, involuntary muscle, glands
somatic: skeletal muscles

general function
autonomic: adjustment of internal environment.
somatic: response to external environment.

efferent pathways
autonomic: two nerve fibres from the CNS to the effector with a synapse in a ganglion
Somatic: one nerve fibre from the CNS to the effector. no synapse and no ganglion

neurotransmitter at effector
Autonomic: acetylcholine or noradrenaline
Somatic: acetylcholine

Control
autonomic: usually involuntary
somatic: usually voluntary

nerves to target organs
autonomic: two sets- sympathetic and parasympathetic
somatic: one set

effect on target organ
autonomic: excitation or inhibition
somatic: excitation

sympathetic system

• fight-or-flight: situations that involve fear, anger, stress.

• increase heart rate and strength of contraction

• dilation of pupil

• increase sweat secretion

• stimulate hormone secretion in adrenal medulla

• decrease movement in stomach and intestines

parasympathetic system

• rest and digest- quiet times

• increase movement of stomach and intestines

• increase secretion of saliva

• constricts muscle walls of urinary bladder

• constricts pupils

homeostasis definition

process of maintaining a fairly constant internal environment

common features of a feedback system

• stimulus: a change in the environment that causes the system to operate

• receptor: detects the change

• modulator: control centre responsible for processing information received from receptor and send information to effector

• effector: carries out response counteracting the effect of the stimulus

• feedback: achieved because original stimulus has been changed by response

negative feedback

feedback that reduces or eliminates the stimulus

positive feedback

reinforces and intensifies stimulus

chlild birth

blood clotting

glycogenesis

formation of glycogen from glucose in the liver

glycogenolysis

breakdown of glycogen to glucose in liver

gluconeogenesis

conversion of fats and proteins into glucose in the liver

lipogenesis

conversion of glucose into fats

lipolysis

breakdown of lipids into glucose

receptor that detects change in blood glucose levels

chemoreceptors in the islets of Langerhans